Regarding DISCO having a low number of new aliens...
I have to agree, it's a smaller amount than previous shows. Even if you go by episode number than season number, which I think is a more fair comparison since DISCO seasons are about half the amount of the legacy shows.
"Labyrinths" is the 63rd episode of DISCO. The other series' 63rd episodes (by production order) are...
TOS: "IS THERE IN TRUTH NO BEAUTY?"
TNG: "Yesterday's Enterprise"
DS9: "VISIONARY"
VOY: "BEFORE AND AFTER"
ENT: "CARPENTER STREET"
By this point of each series, here are the recurring aliens...
TOS had... Orions, Romulans, Klingons, and Andorians. (I don't count others like Tellarites and Medusans because it isn't until later in the series or in other shows that they appear again.)
TNG had... Q, Betazoids, Ferengi, Benzites, and Bolians.
DS9 had... Changelings, Lurians, Hupyrians, Boslic, Vorta, Jem'Hadar, and a myriad of background aliens.
Using VOY as a comparison may not really be fair, since a vast majority of aliens they meet would be one-offs because of the nature of the series. Even still, VOY had more new recurring (two episodes or more) aliens than DISCO: Talaxians, Ocampa, Nacene, Kazon, and Vidiians. (I don't count the Krenim from "BEFORE AND AFTER" because at this point, we only saw their ships.)
ENT had 9 recurring... Denobulans, Suliban, Tandarans, Kreetasans, and Xindi. (I'm counting all 5 types of Xindi as separate, since they were each different.)
By the 63rd episode of each of the previous shows, they had already equalled or surpassed DISCO on just recurring aliens. Most certainly a great deal more one-offs appeared. Which is rather baffling, considering it's taking more time to shoot each episode and more money is spent on DISCO episodes than in the previous ones.